Gigabit-capable Passive Optical Network (GPON) technology is an important technical branch of Passive Optical Network (PON) family, and similar to other PON technologies, GPON is also a passive optical access technology which uses a point-to-multipoint topology.
FIG. 1 is a diagram of the topology of a GPON system according to the related art. As shown in FIG. 1, the GPON comprises an optical line terminal (OLT) at an office side, an optical network unit (ONU) at the subscriber side and an optical distribution network (ODN) and usually uses a point-to-multipoint network structure. An ODN comprises such passive optical devices as a single-mode optical fiber, an optical splitter, an optical connector, etc. and provides an optical transmission medium for a physical connection between OLT and ONU.
In a GPON system, the data transmission in the downlink direction (from OLT to ONU) uses the manner of broadcasting, and each ONU receives all frames respectively and then acquires its own frames according to an optical network unit identification (ONU-ID), a G-PON encapsulation method-port identification (GEM-Port ID) and an Allocation-ID.
FIG. 2 is a schematic diagram of a structure of a downlink frame of GPON according to the related art. As shown in FIG. 2, the downlink frame of GPON comprises a physical control block downstream (PCBd) and a payload. The payload part comprises a plurality of G-PON encapsulation method (GEM) frame headers and GEM payloads. The GEM frame header comprises four parts which are a payload length indicator (PLI), a Port ID, a payload type indicator (PTI) and a header error control (HEC).
In the downlink direction, after having received a GEM frame transmitted by an OLT, an ONU first performs a HEC check. If the HEC check result is incorrect, then the ONU discards the GEM frame, and if the HEC check result is correct, then the ONU judges whether the GEM frame is transmitted to itself according to a PORT ID in the GEM frame header. If it judges that the frame is not transmitted to itself, then the ONU discards the GEM frame, and if it judges that the frame is transmitted to itself, then the ONU receives contents of a corresponding GEM payload of this GEM frame header.
In the uplink direction, after having received a GEM frame transmitted by an ONU, the OLT first performs a HEC check. If the HEC check result is incorrect, then the OLT discards the GEM frame, and if the result is correct, then the OLT receives contents of a corresponding GEM payload of the GEM header.
When the transmitter does not want the receiver to receive data of a specific time, for example, when an OLT does not have sufficient data to be transmitted to an ONU or an ONU does not have sufficient data to be transmitted to an OLT, the existing relevant art uses the manner of the transmitter transmitting idle frames to the receiver, in which, the idle frame is a frame header of a GEM frame the value of which is 0xB6AB31E055, and since the length of the idle frame is comparatively shorter, the receiver needs to resolve the idle frames one by one and the efficiency is rather low.
The existing relevant art does not provide an effective method for handling idle bandwidth, for example, a method of how the transmitter transmits a GEM frame and how the receiver resolves the received GEM frame.